Shock and vibration isolation concepts through use of dynamic, multi-degree-of-freedom mechanical systems

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Abstract

Shock and vibration isolation continues to be an area of great interest to structural designers and to mount manufacturers. When the input disturbance is single-frequency or narrow-band, several techniques are available to limit vibration; e.g., vibration absorbers, use of active or passive damping or structural redesign. However, when the input disturbance is transient in nature or broadband, these isolation strategies are of limited effectiveness. Isolation systems are often modeled as single-degree-of-freedom systems, from which a qualitative picture of the design principles and tradeoffs can be viewed. The design space of isolation systems can be greatly expanded if one considers “dynamic” isolation systems. Passive, dynamic mounts can be thought of as multi-degree-of-freedom collections of springs, masses, and dampers. Such systems can be thought of as “mechanical filters” that attenuate and modify the shock disturbances before the disturbance reaches the isolation component. This dissertation explores several different multi-degree-of-freedom concepts for shock and vibration isolation; some of the systems are purely translational, others contain translational and rotational motion, some are linear while others exhibit varying degrees of nonlinearity. It is shown through numerical simulations, analytical approximations, and experimentation that the multi-degree-of-freedom mount designs can be very effective in accomplishing simultaneous shock and vibration isolation objectives with relatively simple, practical designs.